Radiotelegraph system



Jan, 13, 1925.

J. a. BRADY RADIOTELEGRAPH SYSTEM 3119a Aug. 14. 1923 2 Sheets-Sheet 1 Si nqlin 5 t 9 Impases v Stoglmgglses Impuises FREQUENCY TIME Inventor Jan. 13, 192 1,523,377

J.B.BRADY RADIOTELEGRAPHSYSTEM Filed Aug. 14,1925 2 Sheets-Sheet 2 FREQUENCY LNEBHHO 0 lnuentr Patented Jan. 13, 1925.

UNITED STATES PATENT OFFIC.

JOHN B. BRADY,

OF SOMERSET, MARYLAND, ASSIGNOR T MORKRUM COMPANY, OF

CHICAGO, ILLINOIS, A CORPORATION OF MAINE.

RADIOTELEGRAPH SYSTEM.

Application filed August, 14, 1923. Serial Ito. 657,410.

To all whom it may concern.

Be it known that I, JOHN B. BRADY, a citizen of the United States, residing at Somerset, county of Montgomery, and State of Maryland, have invented a certain new and useful Improvement in Radiotelegraph Systems, of which the following is a specification.

My invention relates broadly to radio communication and more particularly to an automatic system of radio telegraphy wherein signals are automatically transmitted from a central radio station and received directly in print at any number 'of outlying receiving stations.

Oneof the objects of myinvention is to provide an automatic radio telegraphic communication system wherein a central radio station is arranged to distributemessagesto any number of outlying stations simultane-v ously, placing the received signals directly.

in print at each of the several stations with automatic means for controlling the apparatus without the attention of a skilled operator.

Another object of the invention is to provide an automatic radio telegraphic transmission system for signalling with code characters comprising characteristic groups of impulses and also for transmitting impulss at a frequency or tone quality differing from that at which thecharacters representing the. parts of a message are U transmitted for effecting "at a distant receiver, the starting of the automatic printer apparatus for recording a message to be transmitted. 1

A further object of the invention is to provide a selective system of automatic radio ommunication whereby a particular receiv'-' ing station only or a group of receiving stations may be selected and a particular mes- 1 sage transmitted to that station or group of stations to the exclusion of other stations. I Another object of the invention is'to provide an automatic printer receiving apparatus which requires a minimum'of expert attention and which is automatically started before the beginning of I a message and stopped after completion of the message entirely under controlof the distant station delivering the message sent out from the transmitting station directly in printed form.

My invention will be more clearly understoodfrom the following specification and by reference to the accompanying drawings in which: v

Figure 1 shows a diagrammatic arrange-. ment of a radio transmitter and automatic transmitter control; Fig. 2 is 'afragmentarv cross. sectional view of the automatic transmitter control board showing ,the connec tions of the start and stop control key with the radio transmitting apparatus of Fig.1:

Fig. 3 shows another circuit arrangement of the transmitting keyboard and the trans mitting apparatus wherein the transmitter is modulated at 'a diiferent tone frequency when transmitting thestarting and stopping signal to the distant-station; Fig. 4 is a fragmentary side elevation partially broken away showing the arrangement of the starting and stopping key with cooperating contacts, and circuits connected with the transmitter: Fig. 5 is a theoretical diagram showing the difference in either wave length or tone frequency which mayexist between the start 1 and stop impulses; Fig. 6 is a diagrammatic arrangement of the receiving circuits of the automatic printer" receiver showing the arrangement of the starting and stopping c rcuits controlled from the"'distant-t-ransm1tting station; and Fig. 7 isatheoretical diagram representing the electrical characteristics vof the control circuit at the receiver.

This invention may employ various kinds of automatic printer equipment but for the purposes of illustration I have selected the teletype as manufactured by the Morkrl mi' stood that signals may be stored on a perforated strip and automatically, transmitted at high speed. Signals can also be received in this system on a page type of apparatus al-.

though a paper tape printer has been represented at the receiver for purposes of 111115- tration'.

- connected to excite the antenna system.

Various arrangements of electron tube transmitter' circuits may be employed or an. arc generator or alternator or other form of sus tained' wave transmitter may be employed. Signals may be produced by breakingthe grid circuit of the oscillator through relay-6, the coils of which are controlled through a local battery circuit. by the transmitter'contacts 7 and 8 on the teletype keyboard base 10. The details of this construction are set forth in an application for patent filed by Charles L. and Howard L. Krum, Serial No. 477,012? filed June 15, l92l, and Serial No. 673,273, filed November 7, 1923, and also in John B. Bradys Patent No. 1,485,212,=dated February '26, 1924. At the transmitter, contacts such as 7 and 8 are operated by a motor driven cam shaft and are controlled in op eration by a series of selecting bars 11 extending beneath a set of keys 12, each key. being arrangedto operate a different combination of selector bars. The keys also control a clutch whereby when, any key is depressed the cam shaft is driven through one revolution by the motor to operate the contacts, such operation being variably controlled by the selector bars so that the circuit controlled by the contacts is either opened or closed during a ,defin te number, preferably five, of successive definite time intervals for each signal. In this way thirtyone different signals comprising groups of impulses extending through a definite. number of successive time (intervals can beradiated from the antenna system. One of the key levers 14 of the keyboard is employed i as a control key' for selecting, starting and stopping a distant receiver or group of receivers. This key lever 14 is arranged to. make contact with contact point 15 when the key lever is depressed against the action of spring 16,- The contact 15 is well insulated from the keyboard base 10 and connections are taken from the key lever 14 as indicated at 17 and shunted across a portion of the an-- tenna circuit represented at 18. This shunt path may be across an inductance 01' a capacity suflicient to shift the frequency of the radiated energy slightly of the impulses transmitted when the key 14 is depressed.

In Fig. 3 I ha e illustrated the arrangement for shifting he tone frequency of the starting and stopping signal controlled key lever 14. The transmitter circuit may include an electron" tube oscillator and av modulator 20. A pair of. continuously driven buzzers 21 and 22 of differing tone frequency are provided. A localcircuit 24 connected to the terminals 26 of the teletype pletes the circuit through the contacts 7 and 8 at all times that key lever 14 is in its normal up position. In the operation of the radio transmitter with the key lever 14 in the normal up position the transmitted im pulses are modulated at the tone frequency generated by buzzer 21. When, however the key lever 14 is depressed for controlling the selection, starting and stopping of a distant receiver or group of receivers the circuit through buzzer 21 is broken as key lever 14 separates from contact 27 and the circuit is shifted as .the key lever connects with contact 15 through buzzer circuit 22. The impulses from the radio transmitter will now be modulated at a different tone frequency than when the other keys 12 of the keyboard are being depressed in the process of transmitting a message while key lever 14 is in its upper position.

The theoretical diagram in Fig. 5 illustrates the principle of operation of the transmitting circuits heretofore described. The transmitting wavelength or tone frequency is represented by the ordinate while the time is designated by the abscissa. Thus in selecting and starting a distant receiver the 'first series of impulses transmitted bydepressing key lever-14 may be of a relatively lower tone frequency or slightly shorter wavelength as indicated 'at A than that at which the signalling impulses are transmitted in depressing the various keys 12 as rep-h resenteui bflihe horizontal curve .13 while the stop' signal produced by depressing key lever 14 returns again to the value denoted by curve C.

The circuit-arrangements gt a distant re- 6. ach printer receiver are shown in igj ceiving station may be tuned and locked for operation ata particular frequency. The

radio frequency energy collecting system may be a-loopor an-antenna system shown 'at 30. A master cutout switch is employed as shown at 31 which when revolved and set in a counter clockwise direction completes a circuit connection from the antenna 30 through primary coil 32 and ground 33 at the same time that contacts 34 close;a power circuit 35 through primary winding 36 of transformer 37.- The apparatus may be protected against atmospherics by re-- volving switch 31 in/ a clockwise direction shorting antenna 30 to ground 33 and. cutting off the power from transformer'37.

The primary winding 32 is coupled with *7 "The transformer 37 ,may

tuned circuit 38 which connects with the radio receiving apparatus. The receiver is designed for operation at maximum efficiency on the part icular signalling frequency and may comprise a radio frequency amplifier made up of electron tubes 39, 40" and 41, detector 42' operating with driver 43 and the two stage audio frequency amplifier 44 and 45. The, impulses reproduced by this amplifier are conveyed to the input circuit of a selectively responsive power tube relay 46 having a timed input circuit 47 and a sharply responsive mechanical relay 48 in the plate circuit of parallel connected tubes 49 and 50. A negative bias is applied to the grid circuit from direct current source 63.

'A teletype printer receiver 51 is arranged},

to have its teletype magnet coils 52'controlled by the relay 48 to mechanically reproduce the impulses transmitted from thedistant station and actuate the automatic printing apparatus The local circ uit ;is given extremely small electrical inertia by inclusion of resistance 53 in the circuit in series with the source of direct current supply which is obtained from a tapped Winding 54 on auto transformer 55.

By reasonof the multiplicity of circuits at the receiver the power for the electron tube circuits and the circuits of the apparatus to be hereinafter described may be fed from a common source, where practicable, in a manner somewhat similar to that shown in Lowell and Dunmore Pateht 1,455,141 dated ,May 15, 1923. The transformer 37 is energized from the alternating current supply circuit 35 through primary winding 36. have secondary windings 56, 57, 58, 53, and 60 which supply the various circuits to be hereinafter described. Winding 56 supplies the filament lighting circuits for the several electron tubes in the system. Winding 57 supplies energy which is rectifiedby two electrode tubes 61 and furnished as direct current across auto transformer 55. Winding 58 supplies heating current to the filament of the rectifier 61., Winding 59 supplies energy which is rectified by. two electrode tubes 62.

and delivered as direct current across auto transformer circuit'63. The filament circuit of the tube 62 is heatedfrom coil 60.

The motor 64 on the teletype base 51 of the printer receiver operates the automatic printer equipment such operation being controlled by the'magnet 52 as set forth in the applications apdqaatent above noted. The speed of themotor is maintained in proper relation with that of .themotor at the distant transmitter by' -means 'of electron tube control circuit 65 more fully described in my copending application Serial Number 657,061 filed Aug. 13, 1923;

The starting and stopping of the motor 64 under control of a distant station is accomplished by the reception of impulses of particular characteristics through selective circuit 66. The circuit 66 is connected to .the last stage of audio frequency amplificaistic of this circuit is shown in Fig. 7. A

selective tone frequency power tuberelay 68 is connected to the circuit 66 and arran ed to be actuated only by the selection, starting and stopping impulses whereby mechanical relay 69 is selectively operated. A negative bias is applied to the grid circuit of the tubes 68 from directcurre'nt source 63. A localcircuit is controlled by relay 69 supplied with direct current from tap 54 on auto transformer 55 and made responsive -to a minimum electrical inertia by the inclusion of resistance 70. The local circu'it terminates in brushes 71 and 72 which contact with. collector rings 73, 74, 75 and 76 secured on plunger member 77. The plunger member is polarized or arranged to be shiftedlongitudinally forward or backward in frame 78 by solenoidal coil 7 9. The coil 79 is energized in such a direction that the plunger rod will move either forward or backward by reason of the direction of the current delivered to the solenoid through bruslies 71 and 72 and contacts 73, 74, 75, and 76 which are connected to reverse or change the connections of the plunger operating coilwith respect to the external supply circuit. In the arrangement shown. the contacts 73 and 76 are connected together and to one end of -the solenoidal coil 79. Contacts 74 and 75 are connected together and to .the opposite end of the coil 79. The plunger member 77 carries a .connector bar 80 at itsextre 't 1 which is moved either into its full line position or its dotted lineposi tion under action of spring member 81 pivotally 'mounted on support 82. The

, spring member 81. is U shaped in contour and serves to carry connector bar 80 in either of its extreme positlons on receipt of the starting or stopping impulses which imparts the first longitudinal force to the plunger .member 77. lVhen the connector80 is in its dotted line positionthe contacts 83 are shorted closing the circuit through the motor from a source of direct current which may be obtained from a suitable ta-p 85 on. auto transformer 55.

In the operation of the system herein detained constantly lighted with the radio frequency energy collecting system set for the particular wavelength at which the printer signals are transmitted. The driving motor 64 at the receiver is stationary. When the transmitter desires to record a message in print at the distant receiver the start key 14 in Fig. 1 is depressed to transmit impulses of a particular frequency. These signals are received by the antenna system 30 and amplified bythe radio frequency amplifier 39, and 41. The signals combine with the lbcally produced oscillations from generator 43 to produce a succession of beat notes having a frequency to which circuit 66 and rely 68 are responsive but to which relay circuits 46 and 47 are not responsive. The connector 80 is normally open but when mechanical relay 69 closes, the solenoid 79 is energized to impart an initial force to plunger member 77 in forward direction. When this initial force is received the spring member 81 carries the plunger 77 to the extreme end of its path of travel closing contacts 83 which completes the circuit of and starts the driving motor 64 into operation. The various keys 12 at the distant transmitter are then depressed spelling out the message intended for that particular receiving station. The beat note produced by combination of the received signalling impulses and the local oscillations from generator 43 has now shifted and this note cannot pass through the selective circuit 66 and relay 68. Mechanical relay 69 therefore remains inactive. On the other hand relay circuit 47 and 46 are highly eflicient to this note and mechanical why 48 follows the successive groups of impulses delivering them to teletype magnet coils 52 which in its corresponding movements controls the inotor driven printer so as to print characters represented by each particular combmation of impulses. When the period of transmission is completed the key 14 at the distant transmitter is again depressed sending out impulses again resulting in a beat frequency at the receiving station to which relay circuit 47 and 46 is opaque. Relay 69 is operated however closing its local con trol circuit. When the plunger member 77 moved longitudinally in closing contacts 83 the circuit connection to solenoid 79 was thereby opening the motor circuit bring ing it to rest." It will be observed that the apparatus is now in condition to be instantly started for the direction of current in solenoidal winding 79 will be such as to give plunger member 77 and initial longitudinal force forward enabling spring member 81-to become effective and the cycle of operations performed as above described.

When the transmitter employed in Fig. '2

is used the selecting, starting and stopping impulses aremodulated at the tone frequency of buzzer 22. At the receiver the above outlined to be performed. During the transmission of the printer signals the impulses are modulated at the tone frequency of buzzer 21 which tone frequency readily operates relay circuit 47 and 46 at the receiver actuating the automatic printer mechanism to set down the signals directly in print.

It will be understood that control mechanism may be placed in different receiving stations and a corresponding number of control keys arranged in the central transmitting station whereby any particular group of outlying receiving'stations or .individual receiving station may be selected and the printing mechanismstarted and stopped.

The control mechanism at the different receiving stations may be varied in construc-' tional details and othermodifications of the system made Without departing fromthe spirit of the invention as covered by the appended claims. i

means for radiating said oscillations in groups of impulses of energy, a receiving station having means for receiving said impulses, an automatic prlnter arranged to be operated by said impulses, means for drivmg said automatic printer and means at said transmitter for radiating impulses of" differing characteristics for separately controlling said driving means and v actuating. sald automatic prlnter.

2. A system of radio communication coinif prising in combination a radio transmitter having a source of sustained osc llations,

{means for radiating said oscillations in groups of impulses of energy, means for receiving saidoscillations, an automatic printer arranged to. respond to said impulses, means for driving said automatic printer, and means at said radio transmitter for radiating impulses preceding and following said printer impulses whereby said driving ,means at said receiver may be started and stop ed.

3. A system 0 radio communication commeans for radiating prising in combination a radio transmitter,

a plurality of means for controlling said transmitter for radiating a plurality of groups of impulses of energy, a radio re-.

celvmg apparatus, an automatic printer connected thereto and arranged to be actuated by said impulses, driving means for said automatic printer and means at said transmitter for causing the radiation of a group of preliminary signals for starting said driving means at said receiver and, then shifting to said aforementioned plurali of means whereby signals may be sim taneously printed at said receiver and means for causing the radiation of a group of concluding signals for stopping said driving means at said receiver at the end of a message.

- 4. A system of radio communication comprising in combination a radio transmitter having a source of sustained oscillations, means for causing the radiation of said oscillations in groups of impulses of energy, a receiving station, means for receiving said oscillations, an automatic printer actuated thereby, driving means for said printer and means connected in circuit with said driving means selectively controlled from said transmitter for starting and stopping said driving means whereby said automatic printer may be started from rest and a message printed and returned to rest at the conclusion of said message under control of said radio transmitter.

5. A stem of radio communication comprising 1n combination a radio transmitter having a source of sustained, oscillations,

means for causing the radiation of said oscil-' lations in groups of impulses of energy, a

receiving station, means for receiving said oscillations, an automatic printer actuated thereby, driving means for said printer, means connected with said receiving means and in circuit with said driving means whereby said driving means may be started and stopped independently of said impulses actuating said automatic printer by signals transmitted from said radio transmitter whereby said automatic printer may be started from said transmitter by signals independent of said printer impulses and a message delivered by means of said 1mpulses and the automatic printer brought to rest at the conclusion of said printer imp se 6. A system of radio communication comprising 1n combination a radio transmitter, impulses of energy at a plurality of different frequencies, a receiving apparatus having electron tube circuitsresponsive, to all of said frequencies, an automatic'printer actuated by said impulses when transmitted at one of said frequencies, driving means for said automatic printer and means under'control of said impulses when transmitted-at another frequency for starting and stopping said driving means.

7. A system of radio communication comprising in combination a radio transmitter, means for radiating impulses of energy on a single wavelength at a plurality of difi'erent tone frequencies, a receiving apparatus having electron tubecircuits responsive to all of said tone frequencies, an automatic printer actuated by said impulses when transmitted at one ,of said tone frequencies, driving means for said automatic printer and means under control ofsaid impulses when transmitted at another tone frequency for starting and stopping said driving means.

A system of radio communication com-- prising in combination a 111K110, transmitter,

means for radiating impulses of energy on a single wavelength at a plurality of different tone frequencies, a receiving.

apparatus having electron tube circuits responsive to all of said tone frequencies, separate circuits each responsive to only a single one of said frequencies, an automatic printer connected to one of said circuits and actgated by said impulses when transmitted at. one of said tone frequencies, driving means for said'automatic printer-and means connected to another of said circuits under control of said impulses when transmitted at another-tone frequency for starting and stopping said drivin means.

S A system of radio communication comprising in combination a radio transmitter having a source of sustained oscillations, a keyboard'for controlling the radiation of .said oscillations in impulses of energy, means for receiving said oscillations, an automatic printer arranged to respond to sald impulses,

means for driving said automatic printer and means on said transmitting keyboard for causing the radiation of impulses differing in character from said printer impulses and receding and following said printer impu ses whereby said driving means at said receiver may be started and stopped.

10. A system of radio communication comprising in combination a radio transmitterhaving a source of sustained oscillations, a keyboard having a plurality of keys for causing the radiation of said oscillatlons in impulses of energy, a receiving station, means for receiving said oscillations, an automatic printer actuated thereby, driving means for said printer and means connected in circuit with said driving means selectively controlled by one of said keys on said keyboard at said transmitter. for starting and stopping said driving means whereby said automatic printer may be started from rest and a message printed and said prlnter resage under control of said radio transmitter.

11. A system of radio communication comprising in combination a radio transmitter having means for radiating code groups of impulses of energy of one character, and special impulses of another character, and a receiver having separate relays selectively responsive respectively to the impulses of difierent' character, a motor driven automatic printer controlled in operation by one of said relays and means under control of the other of sand relays for starting and stopping said motor.

JOHN B. BRADY. 

